A lockdown on Yale campus ended early Monday evening after New Haven Police said that they couldn’t find an on-campus gunman that an anonymous caller had reported. After no sign of a gunman, they are leaning to the conclusion that the report was a hoax.

Chief Dean Esserman said that he hopes to track down the caller.

Police had searcheddoor-to-door on Yale University’s campus earlier Monday for an unknown gunman, after reports of his sighting on or near campus Monday morning prompted a lock-down. Those on campus were ordered to “shelter in place” during the search even though there had been no reports of shootings or injuries.

An earlier email from the university said New Haven police had received a call at about 9:30 a.m.”from an unidentified man claiming ‘his room-mate’ was en route to ‘Yale’ with the intent of shooting people,” and that police are interviewing “witnesses who reported seeing a man with a long-gun either on or within close proximity to the campus.”

Earlier, SWAT teams, New Haven Police, and Yale Police swarmed Old Campus, the center of Yale’s campus. Classes were not in session on Monday.